1. Field of the Invention
The invention relates generally to the field of communications. More specifically, the invention relates to mobile communications systems and networks.
2. Description of the Related Art
In cellular networks such as Global Systems Mobile (GSM), several types of messages can be communicated, such as control or data messages. In the case of GSM, message types are communicated using Service Access Point Identifiers (SAPI) at the xe2x80x9cdata linkxe2x80x9d layer (xe2x80x9cdata linkxe2x80x9d is specified in the well-known Open Systems Integration (OSI) networking model). Control information, such as timing and handshaking signals, which are transparent to users of the GSM network, are communicated using the SAPI0 (SAPI zero) interface. Short Message Services (SMS) are short, fixed-length messages (e.g. a string of 160 characters), such as paging messages, and are communicated using SAPI3 (SAPI three). Further, GSM uses several types of xe2x80x9cchannelsxe2x80x9d (communication pathways separated by frequency/time characteristics) for communicating messages over the network. Current practice allows for SAPI3 messages to be transmitted on only two such channelsxe2x80x94Slow Associated Control Channel (SACCH) and Slow Dedicated Control Channel (SDCCH). A third channel, Fast Associated Control Channel (FACCH), as well as SDCCH can transmit SAPI0 information. Currently, however, there is no practice for transmitting SAPI3 over the FACCH.
A voice call sent over GSM is handled using the TCH (Traffic Channel), which is the channel defined in GSM for transferring user-to-user data such as voice. For transferring critical information such as certain control data, the voice traffic on TCH is pre-empted by the control data and sent over the FACCH. Thus, FACCH is the mechanism by which control data can utilize TCH for transmission. However, during periods of silence, when none of the connected users (mobile systems) are communicating voice, GSM currently prohibits the transmission of any other data, and makes the voice channel xe2x80x9cdedicated.xe2x80x9d Since human beings are not always continuously talking, it would be advantageous to utilize the silent periods between voice traffic on the same channel for transmitting other types of messages such as paging messages.
Thus, there is needed a solution for utilizing silent periods on a dedicated voice or traffic channel for the communicating of data other than traffic that is currently prohibited.
In one embodiment, the invention provides an enhanced mobile messaging system which has a service point access system configured to send short message service data during discontinuous periods of user-to-user data transmission over the same channel used for user-to-user data transmission.